Production of motor fuel



Spt. 20, 1938.

H. v. ATWELL 2,130,662

PRODUCTION OF MOTOR FUEL Filed Dec. 14, 1935 HYDROOARBGN on.

I cnAc/r/Ns u/v/r I I/VATURAL ans I DEPHLfl-MATING u/v/T i F I I IFRAGT/ONATl/VG wwr V I sou/vs ISO-BUTANE HYDAILCzGEN INCLUDING PLUS MET/KANE 2 -311mm: PROPANE connssv PONDWG ETHANE cums GAs CRACK/N6 UNIT TAR Irma/ammo UNIT I HEAVY POL YMERs GASOLINE AND LIGHTER Hrmmmvs INVENTOR v HAROLD K ATWELL ATTORNEY Patented Sept. 20, 1938 UNITED STATES PATENT or-Flce 2,130,662 PRODUCTION or MOTOR FUEL Harold V. Atwell, White Plains, N. Y., assignor to Process Management Company,

Inc., New

York, N. Y., a corporation of Delaware Application December 14, 1935, Serial No. 54,416

4 Claims.

tane and iso-butane, as well as other hydrocar 10 bons, such as propane and ethane, and the corresponding olefins, such as ethylene, propylene and butylenes. It is well-known that suchnormally gaseous hydrocarbons may be polymerized to form valuable low-boiling normally-liquid hydro- 15 carbons suitable for use as motor fuel, either under heat and pressure alone or in thepresence of suitable catalysts. Such conversion may be accomplished, either by first cracking gaseous parafilns to form gaseous oleflns and then polymeriz- 20 ing the gaseous oleflns in a subsequent stage or by conducting the operation in a'single stage. In all such operations, it is normally desirable to remove hydrogen and methane prior to polymerization.

In operations of this character, the question of whether hydrocarbons having four carbon atoms per molecule shall be retained in the gasoline or subjected to polymerization, and similarly, whether hydrocarbons having four carbon 30 atoms per molecule shall be retained in the polymerized gasoline or recycled for further polymerization, has in many instances been diflicult to answer. On the one hand, it is-sometimes possible to retain these hydrocarbons in the liquid fuel 5 product as such; on the other hand, it is known that hydrocarbons having four carbon atoms per molecule may be polymerized to gasoline-like materials of higher boiling points and high antiknock value.

My invention has for an object the provision of an improved method of obtaining motor fuel by polymerization of hydrocarbon gases, wherein a product of the desired volatility may be obtained without sacrifice of useful starting material for 45 polymerization, together with such additional operative advantages and improvements as may hereinafter be found to obtain:

My invention contemplates segregating nor:

mal butane from gaseous charging stock suitable 50 for polymerization, and retaining this normal bu tane in the gasoline product produced either by cracking or by gas polymerization or both, or removing it. from the system, while delivering valuable iso-butane as well as lower-boiling hydro- 55 carbons, preferably free from hydrogen and methane, to the gas polymerizing unit. My invention further contemplates fractionating the products obtained from the polymerizing operation to retain the normal butane in the polymerized asoline, with recycling of the lso-butane to 5 the gas polymerizing unit.

The attached drawing accompanying and forming a part of this specification shows a flow sheet of my process as it may be applied to the polymerization of normally gaseous products of an oil cracking operation.

Referring to this flow sheet, hydrocarbon oil of any suitable character ranging from crude petroleum to naphtha may be cracked in any conventional manner, the products being dephlegmated to remove tar, gas oil, and other constituents boiling above the desired gasoline boiling-point range.

The remaining products comprising gasoline, normally gaseous hydrocarbons and, fixed gases, such as hydrogen and, methane are then fractionated in such manner as to retain most or substantially all of the normal butane in the liquid product and to recover a fraction consisting largely of hydrogen and methane which may be removed from the system and a third fraction containing most or substantially all of the iso-butane and, if desired, propane and/or ethane, together with the corresponding oleflns, propylene and ethylene. Butylones, if present, are difficult to include entirely either in the liquid fraction or the intermediate fraction and in most cases the butylenes will be partly recovered in the gasoline fraction and partly in the intermediate fractionalong with the iso-butane.

In order to accomplish the above separation between normal butane on the one hand and isobutane on the other, a relatively, close vdegree of fractionation or rectification is required. My invention is not limited to the particular manner in which this fractionation is accomplished and 40 any suitable apparatus or method for this purpose may be employed. It may be mentioned, however, that apparatus such as that shown in U, S.

Patents 2,004,011 and 2,003,308, bothto Podbielniak, may, if desired, be employed in order to effect this separation. The separation of the hydrogen and methane is less difficult and may be accomplished in any desired manner. In fact, in many instances a sufllcient-separation of these gases may be eifected in 'the ordinary' separator following the gasoline condenser, while the separation between the normal butane and the isobutane may take place incident to the stabilization of the gasoline fraction.

The intermediate fraction containing asmuch as the iso-butane as may conveniently be separated from the normal butane and liquid fraction is then either subjected to gas polymerization directly or first cracked in order to produce oleilns, such as iso-butylene. Where such gas cracking is employed as a separate operation, temperatures of from 1200 to 1600 F., pressures of from atmospheric to 200 pounds per square inch and short times of contact, preferably not over one or two minutes, will ordinarily be found suitable. The cracked gases are cooled in the usual manner and any tar or liquid products may be removed therefrom.

In any event, the gases separated from the stabilization step, whether or not they have'been subjected to cracking in the manner aforesaid, are subjected to polymerization under elevated temperature and pressure in order to form lowboiling normally liquid hydrocarbons, including di-iso-butylene and other constituents available for inclusion in a motor fuel product. Such polymerization may be conducted under the influence of heat and pressure alone, in which case temperatures of from 750 to 1050 F. and pressures of from 500 to 3,000 pounds per square inch may advantageously be employed or, if. desired, polymerization may be conducted'in the presence of a suitable catalyst, such as a catalyst of the phosphoric acid type or a modified aluminum chloride catalyst, such as sodium'aluminum chloride, or any suitable catalyst of the adsorbent type either alone or in combination with metallic or other surface catalysts. Depending upon the type of catalyst employed, the temperature and pressure will vary widely but in general will be somewhat lower than that required in the thermal type of operation. Temperatures of from 300 to 700 F. and pressures of from 100to 1,000 pounds per square inch may be employed in the catalytic type of operation. Whether. or not a catalyst is employed, the times of contact will ordinarily be .in excess of thirty seconds and, in any event,

somewhat longer times of contact are used than in gas cracking operations intended to produce gaseous oleflns from gaseous parafllns.

After polymerization, the products are cooled and fractionated and are eventually separated into polymers; heavier than the desired motor fuel'product, a motor fuelfraction containing the normal butane, a fixed gaseous fraction comprising largely hydrogen and methane, and an intermediate fraction containing the iso-butane as'well as propane and ethane and the corresponding oleflns, to whatever extentisdesired: This fractionation and stabilization may be carried out independently of the previous step wherein the cracked gasoline is recovered and stabilized or, in many instances, may be carried out simultaneously and concurrently therewith. Thus the attached flow sheet illustrates a process in which gasoline and lighter hydrocarbons are returned to the fractionating or stabilizing unit of the oil cracking installation where separation into fixed gases, motor fuel and an intermediate fraction is effected. It will be recognized by those. skilled in the art that the specific manner of fractionation may in any event be varied as desired. In many instances, the fixed gaseous fraction consisting primarily of hydrogen and methane may readily be recovered by condensing, cooling and separating the products of polymerization under high pressure. The separated liquids may then be flashed with additional heating, if necessary, in order to vaporize gasoline and lighter hydrocarbons leaving the heavy polymers, and

the overhead fraction thereby obtained may be separately fractionated and stabilized or returned to the fractionating and stabilizing unit of the oil-cracking installation as desired.

In any event, however, the separation is so conducted as to retain normal butane in the final liquid product while segregating the iso-butane and any lighter hydrocarbons which it may be desired to include in the feed to the polymerizing unit, and recycling the iso-butane or intermediate fraction to the polymerizing unit.

Any clean stock, such as gas oil produced .in the oil-cracking unit, may be recycled therein and heavy polymers produced in the gas polymerizing unit may likewise be recycled or returned to the oil-cracking unit in order to be converted to lower-boiling hydrocarbons.

Where natural gas is employed as a starting material for the gas polymerization unit, normal butane may be included with any higher boiling hydrocarbons that may be removed from the natural gas, thereby forming what may be generally designated as a natural gasoline or casinghead gasoline" fraction or, where the recovery of such a liquid fraction from the natural gas is not carried out, the normal butane may simply be segregated as such and either removed from the system and used as desired, or it may be delivered to and blended with the final polymerized motor fuel product, the latter being a preferred procedure. v

I am aware that it has been proposed to segregate various constituents of fuel gases, such as butane, propane and ethane, and to subject them separately under individually optimum conditions to gas polymerization, but my invention is not immediately concerned with the segregation of hydrocarbons. for subjection to optimum conditions of temperature and pressure, but is concerned with the point of separation between the constituents to besubjected to polymerization and the constituents desired to be retained in the liquid product or removed from the system without conversion.

I haveobserved that the conversion of normal butane tends to produce relatively low yields of normal. butylene, the polymerization of which tends to give products of relatively low an'tiknock value, whereas the conversion of iso-butane results in the production of a relatively high yield of iso-butylene which. can be polymerized relatively easily to .di-iso-butylene, a product of exceptionally high anti-knock value and one which it is eminently desirable to obtain in the final product. By segregating normal butane and iso-butane from each other, I am able to retain the normal butane in the liquid product, thereby contributing to the volatility of the motor fuel while effecting the conversion of the iso-butane to a far more desirable product from a motor fuel standpoint, and this conversion of iso-bu tane is enhanced by the fact that the conversion takes place in the absence of the relatively difficultly cohvertible normal butane.

While I have variously referred to the production of iso-butylene and di-iso-butylene from iso-butane, it will be understood that my invention is not necessarilyJimi-ted to the production of either of these two-materials, although it is believed that they tend to be formed in the cracking and polymerization operations, respectively, considering iso-butane as the original starting material. However, other products may be formed and these particular compounds are mentioned primarily by way of illustration. In general,

however, the conversion of the'iso-com ds is intended by the production of products of greater anti-knock value than that of products obtained by conversion of the normal compounds, due to the differences between the molecular structures of these types of hydrocarbons.

As has been mentioned hereinabove, the gas polymerization step, quent to a gas cracking step. or alone, may be accomplished with or without the use of a catalyst. My invention is, however, especially adapted to the catalyticltype of conversion, inasmuch ascatalytic polymerization in general tends to produce a product of relatively low volatility which is improved in this respect by the inclusion of the normal butane therein as such, while being at the same time improved by the'prodnets of conversion of the iso-butane.

According to my invention, the total' liquid product obtained from polymerization is of higher anti-knockvalue than that obtained under similar conditions by the simultaneous and concurrent conversion of normal butane and lac-butane,

and an optimum conversion per pass is attainable.

In connection with I the polymerization of normally gaseous hydrocarbons produced in the cracking of hydrocarbon oils, it may be observed that most refineries will be found to produce an excess of total butanes over and above that required or even desirable for inclusion in the cracked gasoline product. If ordinary rough fractionating methods are employed and no clear line of separation is observed between the normal butane and iso-butane, considerable amounts of each of these hydrocarbons will then ordinarily be retained in the cracked gasoline product and the charge to the polymerizing coil will also contain both normal butane and iso-butane in fairly closely related amounts. By fractionating more sharply in accordance with my invention, however, the desired volatility may be secured by means of inclusion of the normal butane in the stantially all of the normal butane, a

liquid motor fuel product, while the iso-butane is segregated and subjected to conversion, for which it is more suitable than the normal butane.

It will be recognized by those skilled in the art that my invention in its broader aspects is not limited to the details of the various cracking, fractionating and other process herein but may be variously practiced and embodied within the-scope of the claims hereinafter made I claim:

1. The process of obtaining low-boiling normally liquid gasoline-like hydrocarbons from the products of' cracking hydrocarbon oils which comprises fractionally separating such. cracked products previously freed from constituents of highersboiling points than the desired motor fuel product into a gasoline fraction including subfraction comprising hydrogeh and methane, and an intermediate gaseous fraction comprising isobutane, subjecting'said intermediate fraction to a polymerizingstep wherein it is subjected to elevated temperature and pressure to form normally liquid products, separating products heavier than the desired motor fuel from the products oi polymerization and returning at least a portion of the remaining lighter products, including butanes, to said step whether carried out subsesteps set forth aseous motor fuel product fractional separation 2. The process of obtaininglow-boiling normally liquid gasoline-like hydrocarbons suitable for use as motor fuel from the products of crack ing hydrocarbon oils, which comprises fraction- .ally separating such cracked products, previously freed from constituents of higher boiling points than the desired motor fuel product, into a gasoline fraction including substantially all of the normal butane, a gaseous fraction comprising hydrogen and methane, and an intermediate 'fraction comprising iso-butane, subjecting said intermediate fraction including said iso-butane to a polymerizing step wherein it is subjected to elevated temperature and pressure to form normally liquid products, removing heavy polymers having boiling" points higher than that of the desired motor fuel product from the products of polymerization, and returning lighter products including iso-butane, normal butane and gasoline to said fractional separation step. 4

3. The process of obtaining low-boiling normally liquid gasoline-like hydrocarbons suitable for use as motor fuel fromthe products of cracking hydrocarbon oils, which comprises fractionallyseparating such cracked products, previously freed from constituents of higher boiling points than the desired motor fuel product, into a gasoline fraction comprising normal butane, a gaseous fraction including substantially all of the hydrogen and methane, and an intermediate fraction comprising iso-butane,' subjecting said intermediate fraction including said iso-butane" to a polymerizing step wherein it is subjected to elevated temperature and pressure in the presence of a catalyst eii'ective to promote the polymerization of normally gaseous unsaturated hydrocarbons to normally liquid hydrocarbons to form normally liquid products, removing heavy polymers having boiling points higher than that of the desired motor fuel product from the products .of polymerization, and returning lighter products including iso-butane, normal butanev and gasoline to said fractional separation step.

4. The process of obtaining low-boiling normally liquid gasoline-like hydrocarbons suitable for use as motor fuel from the products of cracking hydrocarbon oils, hydrocarbon oils, fractionally separating such cracked products, previously freed from constituents of higher boiling points than the desired motor fuelproduct, into a gasoline fraction including substantially all of the normal butane,

' a gaseous fraction comprising hydrogen and methane, and an intermediate fraction comprising iso-butane, subjecting said intermediate fraction including said iso-butane to a polymerizing step wherein it is ture and pressure in the presence of a. catalyst eifective to promote the polymerization of normally gaseous unsaturated hydrocarbons to normally liquid hydrocarbons to form normally liquid products, removing heavy polymers having boiling points higher than that of the desired from the products of polymerization, returning heavy polymers to the cracking operation, and returning lighter products including iso-butane, normal butane and Baseline, to said fractional separation step.

HAROLD V. ATW'ELL.

which comprises cracking subjected to elevated tempera- I GER'I'IHCAIE p? TCORRECTIORI Patentlo. 2,150,662.-

I I September 20, 19 H f HAROLDVQA'IWELL; V v

It is hereby c el tified' 'thaterz er appears in the printed specifieation of the above nnmbered patent requining correction as follows: .Page 2, first column, line 1, for "as" first oecurrence; read of; page 5, seeond colu'mn,

- lines 28 and 29, claim 5 strike out the words "comprising normal butane,

a gaseous fraction including sabstantia lly all of the! insert instead including substantially all of the nomal butane, a gaseous fraction comprising; andthat the said Letters Patent should be read with this correction thenein that the same may'conform to the record of the case in the Patent Office, r v

. Signedn-and seal ecl this 15th day of Noveinber, A. D. 19

Henry Van Medals I (Seal) 1 Acting Connnissioner of Patents. 

